/*
 * Copyright (c) 2011-2020, hubin (jobob@qq.com).
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.baomidou.kisso.common.captcha.filter.library;

/**
 * 花边噪点
 */
public class PerlinNoise {

    static int p[] = {151, 160, 137, 91, 90, 15,
            131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69,
            142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0,
            26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88,
            237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165,
            71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
            60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102,
            143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208,
            89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109,
            198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147,
            118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182,
            189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163,
            70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98,
            108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
            251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51,
            145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
            184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236,
            205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215,
            61, 156, 180, 151, 160, 137, 91, 90, 15,
            131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69,
            142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0,
            26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88,
            237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165,
            71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
            60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102,
            143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208,
            89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109,
            198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147,
            118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182,
            189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163,
            70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98,
            108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
            251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51,
            145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
            184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236,
            205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215,
            61, 156, 180};

    public static double noise2D(double x, double y) {
        double fx = Math.floor(x);
        double fy = Math.floor(y);
        double u, v;
        int ix = ((int) fx) & 0xFF;
        int iy = ((int) fy) & 0xFF;
        x -= fx;
        y -= fy;
        int i = p[ix];
        int j = p[ix + 1];
        u = fade(x);
        v = fade(y);
        double grad1 = grad(p[i + iy], x, y);
        double grad2 = grad(p[j + iy], x - 1, y);
        double grad3 = grad(p[i + iy + 1], x, y - 1);
        double grad4 = grad(p[j + iy + 1], x - 1, y - 1);
        return lerp(v, lerp(u, grad1, grad2), lerp(u, grad3, grad4));
    }

    static double fade(double t) {
        return t * t * t * (t * (t * 6 - 15) + 10);
    }

    static double grad(int hash, double x, double y) {
        int h = hash & 3;
        double u = (h & 1) == 0 ? x : -x;
        double v = (h & 2) == 0 ? y : -y;
        return u + v;
    }

    public static double lerp(double t, double a, double b) {
        return a + t * (b - a);
    }

}
